Spontaneously hypertensive rats were treated continuously with either verapamil, aldomet, or dextrose solution from age 3 weeks to 9 months. Blood pressure control was comparable in the two drug groups. Hemodynamic measures of cardiac output, mean arterial pressure, and heart rate were obtained under barbiturate anesthesia at the end of the study. Heart weights adjusted for body weight were significantly reduced by 11% in both groups of treated animals when compared to untreated hypertensive controls. Verapamil, unlike other vasodilators, reduces myocardial hypertrophy.